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- I'd like to introduce our 
guest speaker for tonight

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here at Space Place.

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Tonight I'm very pleased 
to introduce an astronomer

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from the UW 
Astronomy Department,

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but also a friend of 
mine, Eric Hooper.

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Eric came to us,

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he got his PhD at the University 
of Arizona in astronomy,

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and then came here 
after working at

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UT Austin, came here to 
Madison where he's been here

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for a few years now doing 
a lot of different things,

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but including a two-year 
stint as director of the 
WIYN Observatories.

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You might remember the W 
in WIYN is for Wisconsin.

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It's a set of telescopes 
that we manage from here,

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and Eric was the director 
of those for a term there.

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But tonight, he's gonna tell 
us about some of his research

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with the intriguing 
phrase cosmic archeology,

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but I'm gonna turn it 
over to him right now.

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So please welcome Eric Hooper.

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[clapping]

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- Thank you, Jim.

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And thank you everybody for 
coming out this evening.

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I really appreciate it. 
We have a big crowd here.

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I'm gonna start out by 
just giving a shout out

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to the organization 
that's funding this work,

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and that's the National 
Science Foundation.

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They provide funding 
across the country

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for a lot of different 
interesting science,

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not just in astronomy, but 
across the whole spectrum

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of science, technology, 
engineering, and mathematics.

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And I'm not the only 
one on this project.

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So let me introduce some of 
the other cosmic archeologists.

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I've included the pictures 
of our local team here.

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These are all University of 
Wisconsin Madison astronomers.

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The two on the left and right 
are graduate students who,

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of course, do most of the work.

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The person in the middle 
is the PI or the 
principal investigator.

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She's the leader of the grant.

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The other two are faculty 
collaborators of ours.

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But we're not just a 
UW of Madison team.

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There are other people 
I've showcased down 
here at the bottom.

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These are collaborators 
from across the country,

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and as you also see, from 
other parts of the world.

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These are part a large 
international team

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called the Sloan 
Digital Sky Survey.

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We'll talk more about 
that later in the talk,

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so I'm just giving you a little 
foreshadowing of that here.

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And one of the themes about 
this that you're gonna see

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throughout this talk is that 
a lot of modern scientific

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research, including in 
astronomy, is done by teams

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of people, this is actually 
a relatively small team,

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and also utilizing 
a wide variety

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of different technologies 
and techniques.

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That's gonna be part of 
the story of this evening,

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is what those techniques 
and technologies

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we're using to address 
the project I'm 
gonna tell you about.

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Well first, we have to 
deal with that title,

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that weird title 
that Jim alluded to.

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He's really hoping I'm 
gonna explain what it is.

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I know that some of 
you may be thinking,

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"Oh, that guy, this 
is a marketing ploy.

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"He just made up the weirdest 
title he could think of

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"to get a crowd out tonight."

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Well, maybe a little bit.

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But the fun part of 
tonight's talk is

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that it is not completely crazy.

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There's actually 
a grain of truth

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in everything in that title,

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and I'm gonna explain a 
little bit of that here.

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And the entire talk 
is encapsulated, 
really, in the title.

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So it's more than 
just crazy marketing.

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There really is meaning to 
everything that's in that title,

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and I just wanna unpack 
that a little bit here.

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But first, a quick 
story, little anecdote,

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how I actually 
came up with this.

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It wasn't for this talk,

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although the details 
of it for this talk,

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but it occurred to me while 
I was traveling sometime.

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I was flying and I 
was on an airplane.

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And, as often happens, 
you sit next to somebody

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and they ask, "Well, where're 
you going after Chicago?"

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And after you say, "Well, 
I'm going to Kalamazoo

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"and they're going 
to Walla Walla,"

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then the conversation goes to,

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"Oh, well, what do 
you do for a career?"

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And we sometimes get some 
interesting responses

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when we say we're astronomers,

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because there's just not 
that many of us in the world.

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And some people find 
that really intriguing.

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Some people find 
that really strange

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and they don't know what to do.

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and I've often thought, 
"What could I say

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"that would have a 
grain of truth to it

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"that would really make people 
think it's kinda weird?"

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So I've thought, I guess I 
could say, given the project 
I'm working on now,

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I could turn to them.

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I could say, "Yeah, so, I'm

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"a time-traveling 
cosmic archeologist.

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"And by the way, let's talk 
about this on the 15-hour 
flight to Shanghai."

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[laughing] 
All right.

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So let's unpack what 
I actually mean here.

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Clearly the most 
ridiculous sounding part

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of that whole title 
is the archeology.

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I mean, what does astronomy 
have to do with archeology,

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other than they 
both start with A?

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I have heard, oftentimes, 
that astronomers,

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and maybe others, use 
archeology as sort

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of a metaphor for astronomy.

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Here's why.

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Because there is an element 
of looking into the past

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that's inherent in astronomy.

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The reason for 
that is that light,

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and any information 
that comes with it,

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has a finite travel time.

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Now, that may not be readily 
apparent to us in this room

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because the speed of 
light is so rapid,

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but when you're talking 
about the vast distances

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that we are often dealing 
with in astronomy,

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then it starts 
becoming relevant.

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For example, the Sun's 
light that we see,

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is already a few minutes old.

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That's not that far in the past.

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Center of the galaxy, 
when we look at it,

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is over 20,000 years old.

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The nearest large galaxy,

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now we're going over 
a million years old.

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So by having things very far 
away when we look at them,

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we are inherently 
looking into the past.

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Maybe a more 
down-to-earth analogy.

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I don't know if maybe 
today in middle school

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and in elementary school 
they don't do this,

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but in my time kids would 
pass notes to each other.

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So here's the analogy.

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Somebody starts passing 
around the note around school

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that so-and-so likes 
whosie-what-sit.

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And by the time that note 
makes it all the way

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around school, so-and-so 
and whosie-what-sit have 
already broken up.

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So by the time you get 
that, if you're at the end

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of the chain, you have just 
discovered information,

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it's real information, 
but it is lagging in time.

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It's out of date.

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And that is unavoidable 
in astronomy.

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And so that's why 
people often will say,

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"Astronomy's a little bit like 
archeology in that sense."

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But not really.

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There is a difference.

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And in astronomy, when 
you're looking back in time

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at something that is old 
because it's far away,

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it's not that we are digging 
up pieces of the past

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and looking at them 
as they are now.

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It's as though we are 
actually able to look at

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what really happened.

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Take Pompeii, for example, 
on that fateful day

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when Vesuvius blew up.

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It would be as though rather 
than going to Pompeii now

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and unearthing artifacts 
from that time,

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we were able to look 
from a distance and watch

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the life of the 
city in the morning,

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watch the residents go about 
their day on that final day.

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Now, it would not 
be a very clear view

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because it would be 
a long ways away.

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We would not have really good 
images or pictures of it,

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but that's what 
we would be doing.

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We'd actually see 
it going through

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and happening as it occurred.

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So in that sense, it's 
not like archeology.

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That's the time travel 
bit in my title.

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But wait, there is also 
an element of archeology,

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in that what we 
are trying to do,

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and I'm going to 
describe to you,

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is look back in time

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at distant objects and 
look for artifacts.

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So we are doing both.

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It is time traveling 
and it is archeology.

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We're trying to understand 
what has been happening

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with galaxies and the 
black holes they contain,

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at times previous 
to when we see them.

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Why? We'll talk about that.

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So, we're gonna talk

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about a fair number of 
things this evening.

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Big ones are black 
holes and galaxies.

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That's what this whole 
project is about.

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By the way, this project, this 
time traveling archeology,

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this is a field report.

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We're not completely done yet. 
We're in the middle of it.

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We've got a lot of work done. 
This is an update.

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This is like when you're 
watching a show about archeology

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on TV and they are 
just starting the dig

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and they're out in the jungle 
and they're getting hot

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and sweaty and they're 
getting bitten by scorpions,

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that's where we are, we're 
at the scorpion-biting 
phase of this.

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So we're gonna talk 
about black holes,

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supermassive or monstrous 
black holes, and galaxies.

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The black holes living inside

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at the centers of the galaxies, 
how are they connected?

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That's the fundamental 
question that we're after.

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And what have these 
been doing in the past,

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specifically the stars 
that are in the galaxies?

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Galaxies are made up of a 
bunch of different things

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that we'll talk about here 
in a minute, but the stars, 
what have they been doing?

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And what have the black 
holes been up to in the past?

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We're gonna talk about 
some new observations

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with a big radio telescope.

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You may be thinking of 
the one in New Mexico.

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Some people may 
be aware of that.

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A little farther away, 
a little bit bigger.

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As I mentioned, a lot of 
modern science needs multiple

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different approaches 
all integrated together.

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One of the things we're doing 
are massive simulations,

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theoretical work using computers 
to try to understand better

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what we're actually seeing 
with some of these telescopes.

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And also, we're utilizing 
visible light surveys

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of the sky as well.

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So that's where we're 
going this evening.

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Black holes and galaxies.

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I talked about that this 
was gonna be a connection

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between them, a story of 
the connection between them.

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Time traveling in the 
sense of looking backward

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or into the past and see how 
they actually were at time.

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Archeology in the sense that 
we are going to be looking

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at relics in the past of 
yet even in earlier history

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of both the galaxies 
and the black holes.

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But before we dig into 
these connections,

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let's actually talk 
about, remind ourselves

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what are the black holes 
and what are galaxies?

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On the left here,

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is a series of depictions 
of a black hole.

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Little bit hard to 
get a real picture.

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This is more than an 
artist's conception.

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This is actually a 
computer simulation

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of a disk of material 
around a black hole.

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Anybody recognize it?

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It may look vaguely familiar.

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It's a simulation that went

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into the Hollywood 
movie Interstellar.

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So that the filmmakers 
there wanted to have as much

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scientific accuracy 
as they could

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within the constraints 
of the production.

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So one of their major 
scientific advisor,

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who I understand worked 
very closely with them,

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is a fellow named Kip Thorne.

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Kip Thorne recently won 
the Nobel Prize in physics

242
00:10:43,800 --> 00:10:45,800
for working on 
gravity-related things.

243
00:10:45,900 --> 00:10:49,033
So he knows a thing or two 
about black holes and gravity.

244
00:10:49,133 --> 00:10:51,100
He has literally written 
some of the books on them.

245
00:10:51,200 --> 00:10:53,800
He worked with their 
special effects team

246
00:10:53,900 --> 00:10:57,533
to make as realistic as 
possible simulations.

247
00:10:57,633 --> 00:10:59,800
So going down from the top here,

248
00:10:59,900 --> 00:11:02,700
if anybody saw the movie, 
this is closest

249
00:11:02,800 --> 00:11:05,233
to what was actually 
depicted in the movie.

250
00:11:05,333 --> 00:11:06,833
The black hole is 
here in the middle.

251
00:11:06,933 --> 00:11:09,100
More specifically, 
that's its event horizon.

252
00:11:09,200 --> 00:11:12,600
And this material around it 
is called the accretion disk.

253
00:11:12,700 --> 00:11:15,766
It's material flowing 
into the black hole.

254
00:11:17,200 --> 00:11:21,766
This was depicted in the 
movie, but more realistic

255
00:11:21,866 --> 00:11:24,200
are these down here, these two.

256
00:11:24,300 --> 00:11:25,900
These are progressively 
more realistic.

257
00:11:26,000 --> 00:11:29,200
What they put in the movie 
did not have an effect

258
00:11:29,300 --> 00:11:31,900
known as Doppler shifting, 
which changes colors

259
00:11:32,000 --> 00:11:34,366
depending on whether the 
material's moving towards you

260
00:11:34,466 --> 00:11:35,766
or away from you.

261
00:11:35,866 --> 00:11:37,933
And there is also an 
effect of relativity

262
00:11:38,033 --> 00:11:40,133
that makes things moving 
very fast towards you

263
00:11:40,233 --> 00:11:43,933
appear brighter, over here, 
and things that are moving

264
00:11:44,033 --> 00:11:45,666
quickly away from 
you appear dimmer.

265
00:11:45,766 --> 00:11:49,966
So this is how, right 
here, a bit closer

266
00:11:50,066 --> 00:11:53,066
to how the black hole 
would be more realistically

267
00:11:53,166 --> 00:11:55,933
in appearance, but that was 
thought to be a little bit,

268
00:11:56,033 --> 00:11:57,633
potentially too confusing 
to the audience.

269
00:11:57,733 --> 00:12:00,233
I was reading about this, 
interestingly enough,

270
00:12:00,333 --> 00:12:04,166
in a scientific paper, 
in a journal called,

271
00:12:04,266 --> 00:12:06,133
Classical and Quantum Gravity , 
Kip Thorne

272
00:12:06,233 --> 00:12:09,600
and the special effects 
people wrote a paper,

273
00:12:09,700 --> 00:12:12,500
more than one, I think, about 
doing movie special effects

274
00:12:12,600 --> 00:12:14,066
in Classical and 
Quantum Gravity.

275
00:12:14,166 --> 00:12:15,933
It's actually a 
really fun paper.

276
00:12:16,033 --> 00:12:19,133
And down here, finally...

277
00:12:19,233 --> 00:12:24,700
This is an attempt to explain 
why it looks so weird.

278
00:12:24,800 --> 00:12:26,666
Anybody, when they saw 
the movie, wondered

279
00:12:26,766 --> 00:12:29,800
why is there material, if you've 
heard of an accretion disk,

280
00:12:29,900 --> 00:12:33,800
why is it above and below as 
well as from side to side?

281
00:12:33,900 --> 00:12:38,266
It's an effect of gravity 
called gravitational lensing.

282
00:12:38,366 --> 00:12:41,266
This up here is a colored disk.

283
00:12:41,366 --> 00:12:45,100
It's a color swatch that 
changes color radiating outward

284
00:12:45,200 --> 00:12:47,433
and is the same 
all the way around.

285
00:12:47,533 --> 00:12:51,466
If you take this and put it 
in front of the black hole,

286
00:12:51,566 --> 00:12:54,466
because of the warping 
of space time by gravity,

287
00:12:54,566 --> 00:12:56,300
this is what you see.

288
00:12:56,400 --> 00:12:58,966
So this is really just a 
nice, uniform color swatch,

289
00:12:59,066 --> 00:13:01,533
but see how it gets 
distorted around there?

290
00:13:01,633 --> 00:13:04,700
Gravitational effects through 
the warping of space time.

291
00:13:04,800 --> 00:13:07,533
Anyway, that's my little 
introduction into black holes.

292
00:13:07,633 --> 00:13:10,066
By the way, I, and it turns 
out, other astronomers,

293
00:13:10,166 --> 00:13:11,933
had assumed that 
when we saw the movie

294
00:13:12,033 --> 00:13:15,333
that this is what's called 
a stellar mass black hole,

295
00:13:15,433 --> 00:13:18,100
something that has 
relatively, as you will see,

296
00:13:18,200 --> 00:13:20,800
low mass, though it's 
not low by our standards,

297
00:13:20,900 --> 00:13:23,966
a few times the mass of our Sun.

298
00:13:25,066 --> 00:13:29,133
And it's the product of a 
large massive star dying

299
00:13:29,233 --> 00:13:31,033
leads to a black hole like that.

300
00:13:31,133 --> 00:13:32,733
We all assumed 
that's what this is.

301
00:13:32,833 --> 00:13:35,633
Well, in reading about it, Kip 
Thorne actually modeled this

302
00:13:35,733 --> 00:13:37,600
as what's called a 
supermassive black hole.

303
00:13:37,700 --> 00:13:40,466
The black hole that 
was in the simulations

304
00:13:40,566 --> 00:13:43,600
is 100,000,000 times 
the mass of our Sun.

305
00:13:43,700 --> 00:13:46,633
And I was delighted to 
see that, because what I 
am talking about here

306
00:13:46,733 --> 00:13:48,466
are supermassive black holes,

307
00:13:48,566 --> 00:13:50,100
black holes with 
masses of millions

308
00:13:50,200 --> 00:13:52,600
and even billions of 
times the mass of the Sun.

309
00:13:52,700 --> 00:13:55,266
So this is actually a very 
relevant depiction of this.

310
00:13:55,366 --> 00:13:58,633
So that's a bit about black 
holes, supermassive ones.

311
00:13:58,733 --> 00:14:01,633
They live in here, in 
the middle of the galaxy.

312
00:14:03,433 --> 00:14:05,333
We live in a galaxy.

313
00:14:05,433 --> 00:14:07,833
If you go outside, maybe 
later at night if it's clear,

314
00:14:07,933 --> 00:14:11,000
get out where some lights are, 
away from some of the lights,

315
00:14:11,100 --> 00:14:13,733
you can see it's the Milky Way, 
that's our galaxy.

316
00:14:13,833 --> 00:14:15,333
This is not a picture 
of the Milky Way.

317
00:14:15,433 --> 00:14:17,000
Some people may recognize 
this as a picture

318
00:14:17,100 --> 00:14:20,800
of the Sombrero Galaxy taken 
with the Hubble Space Telescope.

319
00:14:20,900 --> 00:14:23,600
It's meant there as 
kind of a generic

320
00:14:23,700 --> 00:14:26,400
but very pretty depiction 
of the galaxy, you see 
some of the parts of it.

321
00:14:26,500 --> 00:14:30,200
You see the fuzz there, the 
lighted fuzz, those are stars.

322
00:14:30,300 --> 00:14:32,133
This is an enormous 
number of stars

323
00:14:32,233 --> 00:14:34,000
whose light's all 
blended together.

324
00:14:35,000 --> 00:14:37,400
The dark plane is a disk of gas.

325
00:14:37,500 --> 00:14:39,400
We have a plane 
in our Milky Way.

326
00:14:39,500 --> 00:14:41,966
Our Milky Way doesn't 
look like this quite.

327
00:14:42,066 --> 00:14:43,566
It is a different 
type of galaxy,

328
00:14:43,666 --> 00:14:45,466
but it does have 
that disk in it,

329
00:14:45,566 --> 00:14:47,000
does have that dust in it.

330
00:14:47,100 --> 00:14:49,700
And then right at the center 
of almost every galaxy

331
00:14:49,800 --> 00:14:52,833
we know about, there is 
one of these monsters.

332
00:14:52,933 --> 00:14:55,533
There is one of these 
supermassive black holes.

333
00:14:55,633 --> 00:14:58,466
So we live in a galaxy.

334
00:14:58,566 --> 00:15:01,333
There's a supermassive black 
hole living in the galaxy,

335
00:15:01,433 --> 00:15:03,233
almost every one.

336
00:15:03,333 --> 00:15:05,733
What does that mean about us?

337
00:15:05,833 --> 00:15:07,100
I can tell you.

338
00:15:07,200 --> 00:15:09,433
There's somebody 
in here tonight,

339
00:15:10,900 --> 00:15:14,933
sitting right now, and there 
is a supermassive black hole

340
00:15:15,033 --> 00:15:17,700
behind you and 
underneath your chair.

341
00:15:19,433 --> 00:15:21,333
One of you, one of us.

342
00:15:22,333 --> 00:15:24,833
Anybody getting nervous? 
[laughing]

343
00:15:24,933 --> 00:15:28,733
You don't have to worry. 
That one person is me.

344
00:15:28,833 --> 00:15:31,166
The supermassive black 
hole in our galaxy

345
00:15:31,266 --> 00:15:34,433
is roughly there.

346
00:15:34,533 --> 00:15:36,800
It's in that direction, 
still below the horizon.

347
00:15:36,900 --> 00:15:38,933
It's not that long ago.

348
00:15:39,033 --> 00:15:41,133
It's okay. I don't have 
to worry about it.

349
00:15:41,233 --> 00:15:42,833
It's a long ways away.

350
00:15:42,933 --> 00:15:46,566
It takes 25,000 years for 
anything to happen to get to us.

351
00:15:46,666 --> 00:15:50,300
And black holes don't have 
some mysterious sucking power.

352
00:15:50,400 --> 00:15:52,100
They're not gonna suck 
an entire galaxy in,

353
00:15:52,200 --> 00:15:53,933
and things have to get 
relatively close to them.

354
00:15:54,033 --> 00:15:55,400
So we're gonna be 
okay with that.

355
00:15:55,500 --> 00:15:58,733
But if you do get 
material close to them,

356
00:15:58,833 --> 00:16:02,500
and that material falls 
into this accretion disk,

357
00:16:02,600 --> 00:16:05,833
hapless stars, unfortunate 
planets that may be around them,

358
00:16:05,933 --> 00:16:08,366
gas, dust, whatever 
happens to get in there,

359
00:16:08,466 --> 00:16:12,866
loses an enormous amount of 
energy. It's falling energy.

360
00:16:12,966 --> 00:16:14,966
It's just like if something 
fell down, it breaks.

361
00:16:15,066 --> 00:16:18,133
Imagine something falling 
with so much more energy

362
00:16:18,233 --> 00:16:19,766
than we can conceive 
of on Earth,

363
00:16:19,866 --> 00:16:22,166
and it releases some 
of that before it falls

364
00:16:22,266 --> 00:16:25,533
into the black 
hole, that can power

365
00:16:25,633 --> 00:16:27,866
a rather remarkable thing.

366
00:16:27,966 --> 00:16:29,933
It's called an active 
galactic nucleus.

367
00:16:30,033 --> 00:16:32,500
It's the visible manifestation, 
and when I say visible

368
00:16:32,600 --> 00:16:34,133
I don't just mean visible light,

369
00:16:34,233 --> 00:16:36,866
I mean all different kinds 
of electromagnetic radiation

370
00:16:36,966 --> 00:16:39,533
as we'll talk about, 
it's the manifestation

371
00:16:39,633 --> 00:16:42,300
of one of these supermassive 
black holes consuming

372
00:16:42,400 --> 00:16:46,433
material and then jetting 
out some of that material

373
00:16:46,533 --> 00:16:47,933
and a lot of light.

374
00:16:48,033 --> 00:16:50,233
And those jets come out 
at very close to the speed

375
00:16:50,333 --> 00:16:53,266
of light and they can be huge.

376
00:16:53,366 --> 00:16:56,000
So getting over to the 
panel on the right.

377
00:16:56,100 --> 00:16:58,466
Now we're putting the 
two of them together.

378
00:16:58,566 --> 00:17:01,133
This is an image of a 
cluster of galaxies.

379
00:17:01,233 --> 00:17:04,033
Each little fuzz ball in 
there is its own galaxy.

380
00:17:04,133 --> 00:17:05,733
It's like the Milky 
Way in which we live.

381
00:17:05,833 --> 00:17:08,100
Some are bigger, 
some are smaller.

382
00:17:08,200 --> 00:17:11,166
Those red plumes, 
that's a false color.

383
00:17:11,266 --> 00:17:12,533
They're not actually red.

384
00:17:12,633 --> 00:17:16,300
They're representing 
radio jets and lobes.

385
00:17:16,400 --> 00:17:19,333
A lot of times the largest 
physical manifestations

386
00:17:19,433 --> 00:17:21,766
of these active galactic nuclei,

387
00:17:21,866 --> 00:17:24,633
these supermassive black 
holes gobbling up material,

388
00:17:24,733 --> 00:17:27,533
sending up these enormous 
jets at close to the speed

389
00:17:27,633 --> 00:17:29,500
of light are in the radio.

390
00:17:29,600 --> 00:17:31,700
I mentioned the radio 
telescope earlier,

391
00:17:31,800 --> 00:17:33,433
so that's where we're 
going with this.

392
00:17:33,533 --> 00:17:36,700
And you can see how much 
bigger sometimes these are.

393
00:17:36,800 --> 00:17:40,300
They can be much 
larger than the galaxy.

394
00:17:40,400 --> 00:17:42,733
They can be a substantial 
fraction of the size

395
00:17:42,833 --> 00:17:45,900
of a cluster of galaxies, 
like is in this case.

396
00:17:56,966 --> 00:17:59,333
So now, what might 
be the connection?

397
00:17:59,433 --> 00:18:01,400
That's where our 
story's leading.

398
00:18:01,500 --> 00:18:06,166
It's the connection between 
black holes and galaxies.

399
00:18:06,266 --> 00:18:09,333
Again, it's a time travel 
story because we're looking

400
00:18:09,433 --> 00:18:11,700
at things that are distant, 
and hence back in time.

401
00:18:11,800 --> 00:18:14,166
It's an archeological 
story because we're looking

402
00:18:14,266 --> 00:18:17,500
at relics back in time 
to try to understand

403
00:18:17,600 --> 00:18:20,100
what has happened earlier 
and earlier in time.

404
00:18:20,200 --> 00:18:23,633
And what we're trying 
to understand is 
how the black holes

405
00:18:23,733 --> 00:18:26,433
and the stars in the 
galaxies might be connected

406
00:18:26,533 --> 00:18:28,433
with each other.

407
00:18:28,533 --> 00:18:31,366
This is why we're 
thinking about this,

408
00:18:31,466 --> 00:18:34,233
because there is growing 
evidence that there is

409
00:18:34,333 --> 00:18:36,366
a very fundamental connection.

410
00:18:37,466 --> 00:18:40,000
The work on the 
left is not ours.

411
00:18:40,100 --> 00:18:42,566
It's a published paper. 
The citation right there.

412
00:18:42,666 --> 00:18:44,500
But it's showing a 
cluster of galaxies.

413
00:18:44,600 --> 00:18:48,566
Again, the light fuzz balls 
are individual galaxies.

414
00:18:48,666 --> 00:18:51,466
The blue is an X-ray image.

415
00:18:51,566 --> 00:18:54,233
We don't see X-rays, but we 
have to represent it somehow,

416
00:18:54,333 --> 00:18:57,000
so it's a false color image. 
The X-rays are blue.

417
00:18:57,100 --> 00:18:58,366
Again, the radio's in red.

418
00:18:58,466 --> 00:19:00,133
You see those 
large radio plumes.

419
00:19:00,233 --> 00:19:04,633
If you look closely, 
the radio plumes

420
00:19:04,733 --> 00:19:07,700
appear to be in areas where 
there's not many X-rays.

421
00:19:07,800 --> 00:19:11,033
The X-rays are tracing the 
hot gas around these galaxies

422
00:19:11,133 --> 00:19:12,400
around this cluster.

423
00:19:12,500 --> 00:19:15,466
The radio plumes 
driven by this AGN

424
00:19:15,566 --> 00:19:19,866
or active galactic nucleus 
have driven out this material.

425
00:19:19,966 --> 00:19:21,933
There's a term called feedback.

426
00:19:22,033 --> 00:19:24,500
This is something that 
people have been getting more

427
00:19:24,600 --> 00:19:27,300
and more interested in, not 
only because of observational

428
00:19:27,400 --> 00:19:29,600
evidence like this, 
but theoretical evidence.

429
00:19:29,700 --> 00:19:31,466
Folks who have been 
getting better and better

430
00:19:31,566 --> 00:19:33,433
at modeling how galaxies form,

431
00:19:33,533 --> 00:19:36,933
they basically create an entire 
universe inside a computer.

432
00:19:37,033 --> 00:19:40,933
They create gas, primordial gas,

433
00:19:41,033 --> 00:19:43,333
add dark matter, 
this mysterious stuff.

434
00:19:43,433 --> 00:19:45,300
We really don't know what it is.

435
00:19:45,400 --> 00:19:46,933
And watch what happens.

436
00:19:47,033 --> 00:19:50,366
And gravity will cause the gas 
and dark matter to collapse,

437
00:19:50,466 --> 00:19:53,100
which will form galaxies, 
stars, et cetera.

438
00:19:53,200 --> 00:19:56,233
They've gotten better 
and better and better at 
this across my career.

439
00:19:56,333 --> 00:19:59,400
It's actually been remarkable at 
how much progress they've made.

440
00:19:59,500 --> 00:20:02,100
But there was a problem.

441
00:20:02,200 --> 00:20:05,600
Stars formed too quickly, 
more than people see.

442
00:20:05,700 --> 00:20:09,600
Too many stars faster than we 
actually see in real galaxies.

443
00:20:09,700 --> 00:20:11,366
What to do about this?

444
00:20:11,466 --> 00:20:13,933
There had to be some way of 
suppressing that star formation,

445
00:20:14,033 --> 00:20:16,633
some kind of feedback 
mechanism that as gas flowed

446
00:20:16,733 --> 00:20:19,866
into the galaxies would 
then puff it back up again.

447
00:20:19,966 --> 00:20:22,366
Two main candidates for 
that, the stars themselves.

448
00:20:22,466 --> 00:20:25,566
Some stars explode, huge 
explosion, super nova,

449
00:20:25,666 --> 00:20:27,833
they blow the gas 
back out or heat it.

450
00:20:27,933 --> 00:20:30,533
The other one's these, 
the active nucleus.

451
00:20:30,633 --> 00:20:34,300
The material flows in, 
it can light up the black hole,

452
00:20:34,400 --> 00:20:37,866
turn on the active galactic 
nucleus, puff out the material,

453
00:20:37,966 --> 00:20:41,733
shut itself off, and maybe 
shut off the star formation

454
00:20:41,833 --> 00:20:43,266
in the galaxy.

455
00:20:43,366 --> 00:20:46,066
This is where we're going. 
It's that connection.

456
00:20:46,166 --> 00:20:48,133
People have been working on 
this to try to understand

457
00:20:48,233 --> 00:20:49,633
this better and better.

458
00:20:49,733 --> 00:20:51,533
It's probably a fundamental link

459
00:20:51,633 --> 00:20:54,066
between the supermassive 
black holes at the center

460
00:20:54,166 --> 00:20:57,866
of galaxies and the stars 
in the galaxies around them.

461
00:20:57,966 --> 00:21:00,700
The specific question 
we're trying to address

462
00:21:00,800 --> 00:21:03,200
is time scale.

463
00:21:04,300 --> 00:21:08,866
Is there any connection with 
when a supermassive black hole

464
00:21:08,966 --> 00:21:10,933
became active, 
like is shown here,

465
00:21:12,800 --> 00:21:14,833
and any star formation events,

466
00:21:14,933 --> 00:21:17,500
the history of the formation 
of stars in the galaxy.

467
00:21:17,600 --> 00:21:18,866
Is there any connection between.

468
00:21:18,966 --> 00:21:20,900
This would indicate 
there would be.

469
00:21:21,000 --> 00:21:23,266
The theoretical work 
indicate there would be.

470
00:21:23,366 --> 00:21:25,400
But what's the timing?

471
00:21:25,500 --> 00:21:28,466
Does the AGN turn the active 
galactic nucleus on first,

472
00:21:28,566 --> 00:21:29,866
same time, afterwards?

473
00:21:29,966 --> 00:21:31,500
How are they relative 
to each other?

474
00:21:31,600 --> 00:21:33,200
Is there always a connection,

475
00:21:33,300 --> 00:21:35,266
or is there really no 
connection in timing?

476
00:21:35,366 --> 00:21:37,133
Is it maybe just a 
little bit that happens

477
00:21:37,233 --> 00:21:38,466
below what we can detect?

478
00:21:38,566 --> 00:21:39,900
So these are the 
type of questions

479
00:21:40,000 --> 00:21:41,433
that we're trying to answer.

480
00:21:41,533 --> 00:21:45,466
So if we're trying to 
see a connection in time

481
00:21:45,566 --> 00:21:47,866
between what the 
black hole is doing

482
00:21:47,966 --> 00:21:50,766
and what the stars in 
the galaxy are doing,

483
00:21:50,866 --> 00:21:53,666
we can't just look at

484
00:21:53,766 --> 00:21:56,366
a galaxy and a black 
hole at the same time.

485
00:21:56,466 --> 00:21:58,000
Well, you can. 
People have done that.

486
00:21:58,100 --> 00:22:00,100
That's done a lot. 
But you're limited.

487
00:22:00,200 --> 00:22:02,033
You're looking at a snap 
shot in time, one time.

488
00:22:02,133 --> 00:22:05,833
Remember, you're looking 
at Pompeii that morning.

489
00:22:05,933 --> 00:22:08,166
You're not seeing 
what had happened

490
00:22:08,266 --> 00:22:11,400
500 years earlier in Pompeii.

491
00:22:11,500 --> 00:22:15,133
For that, you need to 
go back to that morning

492
00:22:15,233 --> 00:22:18,433
in the early 80's and 
go dig up something.

493
00:22:19,533 --> 00:22:21,066
That's the time 
traveling archeology,

494
00:22:21,166 --> 00:22:22,633
and that's what we're 
trying to do here,

495
00:22:22,733 --> 00:22:25,900
is go dig up things and see 
if we can make a connection

496
00:22:26,000 --> 00:22:27,400
in that time scale.

497
00:22:27,500 --> 00:22:29,733
And the plot on the left 
here is just a schematic.

498
00:22:29,833 --> 00:22:31,433
The thing in the middle 
that looks like a sun

499
00:22:31,533 --> 00:22:33,566
is actually meant to represent 
an active galactic nucleus.

500
00:22:33,666 --> 00:22:35,533
That's a supermassive 
black hole.

501
00:22:35,633 --> 00:22:38,333
Over here,

502
00:22:38,433 --> 00:22:41,733
on the right part of 
that, is the outflow.

503
00:22:41,833 --> 00:22:43,666
And it may even 
trigger star formation.

504
00:22:43,766 --> 00:22:46,200
So the idea, the main idea 
people are thinking about now

505
00:22:46,300 --> 00:22:49,033
is that these active 
galactic nuclei may shut off

506
00:22:49,133 --> 00:22:50,866
star formation, but they 
may also trigger it.

507
00:22:50,966 --> 00:22:52,466
That's an idea that's 
been around a long time.

508
00:22:52,566 --> 00:22:54,666
I remember hearing about 
that in graduate school.

509
00:22:54,766 --> 00:22:56,600
So there may be a 
lot going on here.

510
00:22:59,266 --> 00:23:02,166
And this is the question 
I was addressing just here.

511
00:23:02,266 --> 00:23:03,933
What is the time scale here?

512
00:23:04,033 --> 00:23:07,233
So to do this, 
we need a couple things.

513
00:23:07,333 --> 00:23:09,266
This is the archeology again.

514
00:23:09,366 --> 00:23:13,133
We need to be able to trace a 
black hole's activity history.

515
00:23:13,233 --> 00:23:15,800
What has it been 
up to in the past?

516
00:23:15,900 --> 00:23:18,366
Was it active in the past, 
or was it just sitting there?

517
00:23:18,466 --> 00:23:21,400
Remember, it's only 
active if you have 
material flowing into it.

518
00:23:21,500 --> 00:23:23,966
That accretion disk, if 
it runs out of material,

519
00:23:24,066 --> 00:23:25,600
it just sits there.

520
00:23:25,700 --> 00:23:27,366
Also, we need to be able

521
00:23:27,466 --> 00:23:29,333
to trace the galaxy's 
star formation history.

522
00:23:29,433 --> 00:23:32,166
What were the stars doing? 
Do we see a connection?

523
00:23:32,266 --> 00:23:34,733
Was there an episode of 
activity in the black hole

524
00:23:34,833 --> 00:23:38,366
in the past that then shut 
off the star formation,

525
00:23:38,466 --> 00:23:41,133
that then triggered 
the star formation?

526
00:23:41,233 --> 00:23:42,766
Did the star 
formation happen first

527
00:23:42,866 --> 00:23:45,000
and then trigger the 
black hole or shut it off?

528
00:23:45,100 --> 00:23:47,000
How do these things 
connect with each other?

529
00:23:47,100 --> 00:23:49,000
That's what we're 
trying to get at here.

530
00:23:49,100 --> 00:23:52,266
And we can do that with 
a black hole, at least,

531
00:23:52,366 --> 00:23:53,900
the active galactic 
nucleus, we can do that

532
00:23:54,000 --> 00:23:56,800
if we look at them 
with radio light.

533
00:23:56,900 --> 00:24:00,766
Remember, I said those huge 
plumes were radio emission,

534
00:24:00,866 --> 00:24:03,600
particularly at low frequency.

535
00:24:03,700 --> 00:24:07,333
And we need to be able 
to trace the galaxy's

536
00:24:07,433 --> 00:24:10,000
star formation history, 
and we can do that

537
00:24:10,100 --> 00:24:12,800
with visible light observations.

538
00:24:12,900 --> 00:24:15,033
That's the story 
of this evening,

539
00:24:15,133 --> 00:24:16,533
the rest of the evening here.

540
00:24:16,633 --> 00:24:21,100
So getting to how we 
figure out what the stars

541
00:24:21,200 --> 00:24:25,633
have been up to, this 
is a very brief rundown

542
00:24:25,733 --> 00:24:27,633
of a rather complicated topic.

543
00:24:27,733 --> 00:24:29,733
But the principles are okay.

544
00:24:29,833 --> 00:24:32,033
Over here on the left

545
00:24:32,133 --> 00:24:35,100
is something called a 
Hertzsprung-Russell diagram

546
00:24:35,200 --> 00:24:37,066
or a color magnitude diagram.

547
00:24:37,166 --> 00:24:39,366
We don't need to worry about 
the terminology too much.

548
00:24:39,466 --> 00:24:41,766
It's a plot. 
This is color.

549
00:24:41,866 --> 00:24:43,866
They've nicely color-coded it.

550
00:24:43,966 --> 00:24:47,566
This end is red. 
That end is blue.

551
00:24:47,666 --> 00:24:51,433
So it's color, blue to red, 
and up here is brightness.

552
00:24:51,533 --> 00:24:53,433
This is fainter, 
that's brighter,

553
00:24:53,533 --> 00:24:55,233
and these represent stars.

554
00:24:55,333 --> 00:24:59,566
This is the culmination 
of decades of work,

555
00:24:59,666 --> 00:25:02,300
particularly in the first 
half of the 20th century,

556
00:25:02,400 --> 00:25:04,900
to understand, to not 
only measure these things

557
00:25:05,000 --> 00:25:09,033
but understand how 
this changes with time.

558
00:25:09,133 --> 00:25:12,733
And what happens is that 
when a bunch of new stars

559
00:25:12,833 --> 00:25:16,966
are first born, they 
lie all along here.

560
00:25:17,066 --> 00:25:19,100
This is called 
the main sequence.

561
00:25:19,200 --> 00:25:21,833
And the more massive ones, 
the ones that turn out

562
00:25:21,933 --> 00:25:24,900
the more massive ones, are 
brighter and they're bluer.

563
00:25:25,000 --> 00:25:27,433
They gobble up their fuel, even 
though they have more of it,

564
00:25:27,533 --> 00:25:28,866
they are real hogs.

565
00:25:28,966 --> 00:25:33,000
They gobble up very 
quickly, and they expire.

566
00:25:33,100 --> 00:25:34,733
The star dies.

567
00:25:34,833 --> 00:25:36,400
And so from here,

568
00:25:36,500 --> 00:25:38,300
they would move off to 
this other part here.

569
00:25:38,400 --> 00:25:40,600
This is not a talk 
about stellar evolution,

570
00:25:40,700 --> 00:25:42,600
just suffice it to say 
that they go over here

571
00:25:42,700 --> 00:25:44,500
and then they loop 
around over here

572
00:25:44,600 --> 00:25:46,100
and they eventually peter out.

573
00:25:46,200 --> 00:25:48,966
The point is that the older 
the group of stars are,

574
00:25:49,066 --> 00:25:51,800
the more, whoops.

575
00:25:51,900 --> 00:25:54,066
Back that up a bit, 
hit the wrong button.

576
00:25:54,166 --> 00:25:57,733
The more they moved off of 
here to get down to this,

577
00:25:57,833 --> 00:26:02,233
so you can tell the age of 
a group of stars this way.

578
00:26:02,333 --> 00:26:07,933
And this allows you to then 
connect age of lots of stars

579
00:26:08,033 --> 00:26:11,133
and how the galaxy in 
which they live appears.

580
00:26:11,233 --> 00:26:12,866
And this is it over here.

581
00:26:12,966 --> 00:26:17,100
So if we have very young stars, 
a very young group of stars,

582
00:26:17,200 --> 00:26:19,466
that's these blue 
ones over here.

583
00:26:19,566 --> 00:26:21,933
Remember, the young 
ones live up in here.

584
00:26:22,033 --> 00:26:25,600
Very bright, very blue, so 
they dominate the light,

585
00:26:25,700 --> 00:26:28,966
they can dominate the light 
of the whole group of stars

586
00:26:29,066 --> 00:26:30,466
and even the galaxy.

587
00:26:30,566 --> 00:26:33,200
So this is what's called 
a stellar population.

588
00:26:33,300 --> 00:26:35,766
Each of these graphs is 
a stellar population.

589
00:26:35,866 --> 00:26:40,566
What it means here is this is 
brightness, again, vertical.

590
00:26:40,666 --> 00:26:43,400
And this is color, 
specifically wavelength.

591
00:26:43,500 --> 00:26:46,466
So this is blue, what our 
eyes would see as blue,

592
00:26:46,566 --> 00:26:48,400
red, near infrared.

593
00:26:48,500 --> 00:26:50,466
And even though 
these are each coded

594
00:26:50,566 --> 00:26:52,266
by the same color 
all the way through,

595
00:26:52,366 --> 00:26:53,700
it doesn't mean they're 
all the same color.

596
00:26:53,800 --> 00:26:55,500
It's just that this 
one is colored blue

597
00:26:55,600 --> 00:26:57,466
because it's more 
dominantly blue.

598
00:26:57,566 --> 00:26:59,066
It's got more light 
up in the blue

599
00:26:59,166 --> 00:27:00,900
than it does over 
here in the red.

600
00:27:01,000 --> 00:27:02,366
And this is an age sequence.

601
00:27:02,466 --> 00:27:04,066
Young,

602
00:27:04,166 --> 00:27:06,400
old, 
really old.

603
00:27:06,500 --> 00:27:08,600
You can see what happens.

604
00:27:08,700 --> 00:27:12,266
This plot of light, 
this is like a rainbow.

605
00:27:12,366 --> 00:27:14,666
It's a spectrum.

606
00:27:14,766 --> 00:27:18,800
By the way, these tags up 
here, this is showing us

607
00:27:18,900 --> 00:27:21,633
what kind of the key 
ideas here in each figure

608
00:27:21,733 --> 00:27:23,400
and this is where we are 
in the plot, roughly,

609
00:27:23,500 --> 00:27:24,933
just kind of a guide, 
because this can be

610
00:27:25,033 --> 00:27:26,366
a little bit complicated.

611
00:27:26,466 --> 00:27:28,233
So if you're ever not 
sure, or you wake up

612
00:27:28,333 --> 00:27:29,866
and you say, "Where 
is that guy?"

613
00:27:29,966 --> 00:27:32,333
That's where we are. 
Just look at the top there.

614
00:27:32,433 --> 00:27:37,200
So this is the appearance 
of a collection of stars

615
00:27:37,300 --> 00:27:38,966
of a single age.

616
00:27:39,066 --> 00:27:42,233
And a galaxy is made up 
of collections of stars

617
00:27:42,333 --> 00:27:43,633
of different ages.

618
00:27:43,733 --> 00:27:46,166
And so we can combine 
these together.

619
00:27:47,366 --> 00:27:50,666
Principle is we can combine 
these together and form

620
00:27:50,766 --> 00:27:53,566
the rainbow or the spectrum 
of an entire galaxy

621
00:27:53,666 --> 00:27:55,566
made up of components of these.

622
00:27:55,666 --> 00:27:57,566
If you can combine 
them together to see

623
00:27:57,666 --> 00:28:00,366
what a galaxy looks like, 
you can also take them apart.

624
00:28:00,466 --> 00:28:03,600
That's the key, we can take 
a spectrum of a galaxy,

625
00:28:03,700 --> 00:28:06,633
or pieces of a galaxy, 
and pull it apart

626
00:28:06,733 --> 00:28:10,466
into these constituent 
pieces and understand,

627
00:28:10,566 --> 00:28:13,066
in principle, how old 
each of the pieces were.

628
00:28:13,166 --> 00:28:16,733
So that is the 
stellar archeology.

629
00:28:16,833 --> 00:28:20,166
That's figuring out the past 
history of the star formation

630
00:28:20,266 --> 00:28:24,533
in any galaxy for which we 
have sufficiently good data

631
00:28:24,633 --> 00:28:27,433
and a good enough understanding 
of what we're doing,

632
00:28:27,533 --> 00:28:30,066
which is a key that's 
still being worked on.

633
00:28:30,166 --> 00:28:33,100
Most of our project today,

634
00:28:33,200 --> 00:28:34,700
like I said, this 
is a field report.

635
00:28:34,800 --> 00:28:37,866
We're still in the scorpion 
biting, bug stinging,

636
00:28:37,966 --> 00:28:40,233
digging around in the jungle 
phase of the archeology.

637
00:28:40,333 --> 00:28:42,433
Most of what we've 
done so far has been

638
00:28:42,533 --> 00:28:43,966
on the other part, the radio.

639
00:28:44,066 --> 00:28:46,166
I'll come back to 
the stars in a bit.

640
00:28:46,266 --> 00:28:48,666
This is the AGN.

641
00:28:48,766 --> 00:28:51,533
This thing here is 
also a spectrum.

642
00:28:51,633 --> 00:28:53,966
This is a rainbow, 
just like a rainbow,

643
00:28:54,066 --> 00:28:56,000
rainbow when you see it outside, 
it's a spectrum.

644
00:28:56,100 --> 00:28:57,766
It's breaking the light up 
into its constituent colors,

645
00:28:57,866 --> 00:28:59,633
but this is a radio one.

646
00:28:59,733 --> 00:29:03,633
What's up here at the top are 
frequencies and megahertz.

647
00:29:05,000 --> 00:29:09,333
150 megahertz on the 
left, 1,400 on the right.

648
00:29:09,433 --> 00:29:11,666
Now, that may be 
coming out of the blue.

649
00:29:11,766 --> 00:29:13,800
Red and blue colors, 
we're used to.

650
00:29:13,900 --> 00:29:15,866
150 megahertz, 
well, what's that?

651
00:29:15,966 --> 00:29:17,766
So I gave a few 
guidelines up here.

652
00:29:17,866 --> 00:29:21,033
I've listed a few things we 
might be somewhat familiar with,

653
00:29:21,133 --> 00:29:23,933
very high frequency TV, 
the high band of it,

654
00:29:24,033 --> 00:29:25,700
is roughly where it's 
indicated up there.

655
00:29:25,800 --> 00:29:29,466
The UHF channels of 
TV are over there.

656
00:29:29,566 --> 00:29:32,266
And underneath of it, I 
got merged in a little bit

657
00:29:32,366 --> 00:29:35,200
with the labeling 
there, cell phones.

658
00:29:36,566 --> 00:29:40,333
And AM is lower frequency, 
so off to the left,

659
00:29:40,433 --> 00:29:43,833
and Sirius XM radio is higher 
frequency, so off to the right.

660
00:29:43,933 --> 00:29:46,733
So that kind of gives us an 
idea of where we are here.

661
00:29:46,833 --> 00:29:50,833
And I've plotted spectra

662
00:29:50,933 --> 00:29:53,066
of the radio source.

663
00:29:53,166 --> 00:29:54,666
It looks a lot simpler.

664
00:29:54,766 --> 00:29:57,133
So this is similar to, it's 
the same type of thing,

665
00:29:57,233 --> 00:29:59,766
a plot of brightness 
of light with color

666
00:29:59,866 --> 00:30:03,233
as we had before, but this 
one looks a lot simpler,

667
00:30:03,333 --> 00:30:05,966
thankfully, because that 
one's really complicated.

668
00:30:06,066 --> 00:30:08,433
And again, there's 
a sequence of age.

669
00:30:08,533 --> 00:30:11,366
The blue one here is 
for a radio source

670
00:30:11,466 --> 00:30:13,033
that's 10,000,000 years old.

671
00:30:13,133 --> 00:30:15,933
What you see happening here 
is that as you go older,

672
00:30:16,033 --> 00:30:17,866
the key is down there 
in the lower right,

673
00:30:17,966 --> 00:30:21,566
as you go older from 10,000,000 
years to 50,000,000 years

674
00:30:21,666 --> 00:30:24,933
to 100,000,000 years, by 
the way, MYR is mega year,

675
00:30:25,033 --> 00:30:27,800
million years old, to 
300,000,000 years old.

676
00:30:27,900 --> 00:30:31,066
Look at the corresponding 
colored lines.

677
00:30:31,166 --> 00:30:34,333
The young ones are shallow 
and go straight across.

678
00:30:34,433 --> 00:30:37,366
As they progressively get 
older, they get steeper

679
00:30:37,466 --> 00:30:39,033
and there's a turnover there.

680
00:30:39,133 --> 00:30:41,466
So those are two things 
we're gonna see here more of

681
00:30:41,566 --> 00:30:44,300
as we go forward, how 
steep that line is.

682
00:30:44,400 --> 00:30:46,766
Is it shallow? 
That indicates pretty young.

683
00:30:47,966 --> 00:30:50,000
Or is it steep? 
That indicates older.

684
00:30:50,100 --> 00:30:54,800
And also, the location of where

685
00:30:54,900 --> 00:30:57,233
these turnovers have 
happened, like this one.

686
00:30:57,333 --> 00:30:59,733
This one is 
300,000,000 years old.

687
00:30:59,833 --> 00:31:02,033
Notice how quickly it's 
turning over like that.

688
00:31:02,133 --> 00:31:04,133
So we're gonna talk 
about that more.

689
00:31:04,233 --> 00:31:06,800
The steepness of the 
spectrum, the radio spectrum,

690
00:31:06,900 --> 00:31:10,166
and the turnover point, 
the frequency at which 
it turns over.

691
00:31:10,266 --> 00:31:12,333
This, then, is also a clock.

692
00:31:12,433 --> 00:31:14,533
Like what we had for the stars,

693
00:31:14,633 --> 00:31:16,433
this is a clock for 
the active galaxies.

694
00:31:16,533 --> 00:31:19,500
So we can get some idea 
of how old they are,

695
00:31:19,600 --> 00:31:22,133
and even look for relics,

696
00:31:22,233 --> 00:31:24,433
again, the 
archeological reference.

697
00:31:24,533 --> 00:31:29,433
We are looking for not only 
currently active galaxies,

698
00:31:29,533 --> 00:31:31,600
but ones that may have 
been active in the past.

699
00:31:31,700 --> 00:31:35,333
And this is a way to do that

700
00:31:35,433 --> 00:31:37,833
because you can see 
something that was active

701
00:31:37,933 --> 00:31:41,366
a long time ago, 
300,000,000 years ago,

702
00:31:41,466 --> 00:31:45,066
we can still see it, even if 
it's no longer active today,

703
00:31:45,166 --> 00:31:48,400
with the right kind 
of observations.

704
00:31:48,500 --> 00:31:52,066
And that means lower radio 
frequencies, 300 megahertz,

705
00:31:52,166 --> 00:31:56,400
150 megahertz, are considered 
low frequency in the radio.

706
00:31:59,333 --> 00:32:00,766
So getting there.

707
00:32:00,866 --> 00:32:02,666
At the beginning, 
remember, I mentioned there

708
00:32:02,766 --> 00:32:04,566
would be a radio 
telescope in here,

709
00:32:04,666 --> 00:32:06,033
but it's not the 
one in New Mexico.

710
00:32:06,133 --> 00:32:08,700
The one in New Mexico is 
called the Very Large Array.

711
00:32:08,800 --> 00:32:10,800
It's been in a lot of 
commercials, movies,

712
00:32:10,900 --> 00:32:12,333
the movie Contact, for example.

713
00:32:12,433 --> 00:32:14,133
You can tell I'm a 
bit of a movie buff,

714
00:32:14,233 --> 00:32:17,166
especially when it comes to 
astronomical-themed things.

715
00:32:17,266 --> 00:32:19,100
This is a telescope that's 
actually even bigger

716
00:32:19,200 --> 00:32:21,133
than the one in New Mexico.

717
00:32:21,233 --> 00:32:23,966
More dishes, the dishes 
are larger themselves.

718
00:32:24,066 --> 00:32:26,900
And this picture here 
is just a subset of it.

719
00:32:27,000 --> 00:32:29,233
This is only a tiny 
part of the array.

720
00:32:29,333 --> 00:32:32,700
If you look carefully, 
the one in the foreground,

721
00:32:32,800 --> 00:32:36,733
the biggest dish, is next 
to a little white blob.

722
00:32:36,833 --> 00:32:39,166
That little white 
blob is a Jeep.

723
00:32:39,266 --> 00:32:41,666
These dishes are 
45 meters across.

724
00:32:41,766 --> 00:32:44,200
This is near Pune, India.

725
00:32:44,300 --> 00:32:46,466
It's called the Giant 
Metrewave Radio Telescope,

726
00:32:46,566 --> 00:32:50,800
GMRT there stands for Giant 
Metrewave Radio Telescope.

727
00:32:50,900 --> 00:32:54,300
Metrewaves, it's the 
wavelength of the radio waves.

728
00:32:55,766 --> 00:32:59,833
These things will go, this 
will observe wavelengths,

729
00:32:59,933 --> 00:33:03,233
the shortest one 
is about that big.

730
00:33:03,333 --> 00:33:07,300
The longest one is 
taller than Darth Vader.

731
00:33:07,400 --> 00:33:10,766
That's why they say 
metrewave, it's in the meters.

732
00:33:10,866 --> 00:33:13,133
Longer wavelengths 
corresponds to low frequency.

733
00:33:13,233 --> 00:33:14,966
So those are the same thing.

734
00:33:15,066 --> 00:33:16,733
It's a radio interferometer.

735
00:33:16,833 --> 00:33:19,633
We could have a whole talk 
about radio interferometers.

736
00:33:19,733 --> 00:33:21,866
They're wonderful 
things that allows you

737
00:33:21,966 --> 00:33:25,700
to use many dishes, many 
radio dishes, to work as one.

738
00:33:25,800 --> 00:33:27,933
Gives you the clarity of image

739
00:33:28,033 --> 00:33:30,800
that you would have close to it

740
00:33:30,900 --> 00:33:33,133
if you had a single

741
00:33:33,233 --> 00:33:35,800
gigantic radio dish

742
00:33:35,900 --> 00:33:40,066
that was as big as 
the entire array.

743
00:33:40,166 --> 00:33:43,133
So these things are spread 
out over 10's of kilometers

744
00:33:43,233 --> 00:33:45,600
all across this plane in India.

745
00:33:45,700 --> 00:33:48,633
And they work together and 
they can give you an image

746
00:33:48,733 --> 00:33:51,933
that is approaching as crisp

747
00:33:52,033 --> 00:33:55,400
as if you had a giant 
bowl that was 10's

748
00:33:55,500 --> 00:33:57,666
of kilometers across all 
collecting radio length.

749
00:33:57,766 --> 00:33:59,733
That's why they're really neat. 
That's why people use them.

750
00:33:59,833 --> 00:34:02,500
And over here on the 
right is an example

751
00:34:02,600 --> 00:34:05,166
of observations of 
one of our objects.

752
00:34:05,266 --> 00:34:08,266
This is a radio 
galaxy, similar to ones

753
00:34:08,366 --> 00:34:10,333
that I showed earlier, 
not quite as big.

754
00:34:10,433 --> 00:34:12,566
And all the alphabet, 
don't worry about the 
alphabet soup up there.

755
00:34:12,666 --> 00:34:15,300
Those are different 
surveys, we've drawn 
these from our surveys.

756
00:34:15,400 --> 00:34:18,166
The SS in all these things 
stands for sky survey.

757
00:34:18,266 --> 00:34:22,233
So SDSS is a sky survey. 
TGSS is a sky survey.

758
00:34:22,333 --> 00:34:23,766
WINSS is a sky survey.

759
00:34:23,866 --> 00:34:25,900
And then I've indicated a 
couple points of new data.

760
00:34:26,000 --> 00:34:27,766
These are some of 
the data we've taken

761
00:34:27,866 --> 00:34:29,566
and are currently working on.

762
00:34:29,666 --> 00:34:32,133
We just finished the second 
of three observing runs.

763
00:34:32,233 --> 00:34:33,933
The next one will be 
coming up next month,

764
00:34:34,033 --> 00:34:36,366
and then we will have 
all the data we need,

765
00:34:36,466 --> 00:34:39,033
hopefully for one of the 
graduate student's PhD theses.

766
00:34:39,133 --> 00:34:42,100
And so we'll have a lot 
more of this coming in.

767
00:34:43,533 --> 00:34:45,333
All right.

768
00:34:45,433 --> 00:34:46,900
Here's just a quick example.

769
00:34:47,000 --> 00:34:48,733
This is some early results.

770
00:34:50,566 --> 00:34:52,400
I've plotted three 
things up here.

771
00:34:52,500 --> 00:34:54,700
Remember I said that 
one of the key things

772
00:34:54,800 --> 00:34:57,566
is a spectrums shape, this 
is an indication of shape.

773
00:34:57,666 --> 00:34:59,466
Don't worry about what 
the color bar means here.

774
00:34:59,566 --> 00:35:02,466
The key thing is this. 
This is the age.

775
00:35:02,566 --> 00:35:06,433
This is the derived 
product from the spectrum.

776
00:35:08,333 --> 00:35:10,433
That is

777
00:35:10,533 --> 00:35:13,233
100,000,000 years right there.

778
00:35:13,333 --> 00:35:15,966
Green blue is 200,000,000 years.

779
00:35:16,066 --> 00:35:19,233
And so this thing looks like 
it's actually relatively young.

780
00:35:19,333 --> 00:35:22,200
It's around 50,000,000 years 
old, look at the color there.

781
00:35:22,300 --> 00:35:24,533
Now, a key component of any 
type of scientific research

782
00:35:24,633 --> 00:35:26,433
is not only can I put a number,

783
00:35:26,533 --> 00:35:28,400
but understanding how 
precise that number is.

784
00:35:28,500 --> 00:35:30,900
Is it a good number? 
Is it a usable number?

785
00:35:31,000 --> 00:35:33,133
To what degree is it 
good, is it usable?

786
00:35:33,233 --> 00:35:37,300
That comes with precision or 
understanding the uncertainty.

787
00:35:37,400 --> 00:35:39,966
And so this one over 
here on the right

788
00:35:40,066 --> 00:35:43,800
is a ratio of the 
age we determined

789
00:35:43,900 --> 00:35:46,000
divided by how 
uncertain we think it is.

790
00:35:46,100 --> 00:35:48,233
And those numbers are a 
little bit hard to see,

791
00:35:48,333 --> 00:35:50,333
but they range to 
about 10 to 20 there.

792
00:35:50,433 --> 00:35:53,166
So it's 10 to 20, the 
age is 10 to 20 times

793
00:35:53,266 --> 00:35:55,333
what the precision of it 
is, which is not too bad.

794
00:35:55,433 --> 00:35:57,133
We could do a little bit better.

795
00:35:57,233 --> 00:36:00,966
But that is just the 
so-called random uncertainty.

796
00:36:02,333 --> 00:36:05,633
That's if everything 
else was just fine,

797
00:36:05,733 --> 00:36:08,533
just due to the nature of 
the random fluctuations

798
00:36:08,633 --> 00:36:10,666
in the data you get, 
how good the data are,

799
00:36:10,766 --> 00:36:13,866
but there are more than 
random fluctuations.

800
00:36:14,900 --> 00:36:17,866
There are also 
systematic uncertainties.

801
00:36:17,966 --> 00:36:21,500
And I'm gonna make a brief 
but kinda big deal about this.

802
00:36:21,600 --> 00:36:23,366
I'm gonna put it up 
here, systematic errors,

803
00:36:23,466 --> 00:36:25,400
'cause this is important, 
not just in astronomy,

804
00:36:25,500 --> 00:36:28,300
but in any time we're dealing 
with any type of data,

805
00:36:28,400 --> 00:36:29,866
any type of information.

806
00:36:29,966 --> 00:36:32,466
It's not only the 
basic precision of it,

807
00:36:32,566 --> 00:36:35,166
but also how well-- 
what are your assumptions

808
00:36:35,266 --> 00:36:36,833
and how well do you 
know your assumptions?

809
00:36:36,933 --> 00:36:40,233
For example, polling data 
is a commonly-used analogy.

810
00:36:40,333 --> 00:36:43,200
You'll see an error bar 
quoted on most polls.

811
00:36:43,300 --> 00:36:47,200
That's 35% of people like this

812
00:36:47,300 --> 00:36:49,100
and 70% of people like that,

813
00:36:49,200 --> 00:36:51,933
put an error bar plus 
or minus 2% or 3%

814
00:36:52,033 --> 00:36:53,800
is often what you hear.

815
00:36:53,900 --> 00:36:56,133
But that's only the full story

816
00:36:56,233 --> 00:37:01,033
if it's been a 
careful representative 
sample of the people.

817
00:37:01,133 --> 00:37:03,600
If they only call 
up a group of people

818
00:37:03,700 --> 00:37:06,433
who have a particular 
connection with each other,

819
00:37:06,533 --> 00:37:09,933
they may get very different, 
very skewed and biased results.

820
00:37:10,033 --> 00:37:11,800
And that's what we're 
trying to understand here.

821
00:37:11,900 --> 00:37:13,433
The basic techniques I outlined,

822
00:37:13,533 --> 00:37:17,900
the plot of those simple 
radio spectra, are great,

823
00:37:18,000 --> 00:37:19,833
but they sweep a lotta 
things under the carpet.

824
00:37:19,933 --> 00:37:21,566
It's not that anybody's 
been hiding anything.

825
00:37:21,666 --> 00:37:25,333
It's just this is something 
that was developed 50 years ago.

826
00:37:25,433 --> 00:37:26,866
It's a beautiful piece of work,

827
00:37:26,966 --> 00:37:29,466
but the real things 
are so complicated

828
00:37:29,566 --> 00:37:31,266
that you have to make 
certain assumptions

829
00:37:31,366 --> 00:37:32,933
that we know are 
not valid in nature.

830
00:37:33,033 --> 00:37:35,966
The question is, how 
invalid are they?

831
00:37:36,066 --> 00:37:37,400
What will they do?

832
00:37:37,500 --> 00:37:40,200
What do these assumptions 
do that we've made?

833
00:37:40,300 --> 00:37:43,066
And so this is where the 
numerical simulations

834
00:37:43,166 --> 00:37:45,266
I was talking about 
come into play.

835
00:37:45,366 --> 00:37:47,700
We are

836
00:37:47,800 --> 00:37:49,833
using computer models,

837
00:37:49,933 --> 00:37:53,966
basically creating these 
AGN inside of a computer,

838
00:37:54,066 --> 00:37:56,933
letting them age, and 
seeing what happens to them.

839
00:37:57,033 --> 00:37:59,366
And remember, I told you 
earlier that we would be talking

840
00:37:59,466 --> 00:38:02,466
about a couple things here: 
one is the turnover frequency.

841
00:38:02,566 --> 00:38:05,333
That's what this is. 
This is 100 megahertz.

842
00:38:05,433 --> 00:38:08,266
1,000 megahertz, so this is 
the range we're observing.

843
00:38:08,366 --> 00:38:09,900
This is 10 gigahertz.

844
00:38:10,000 --> 00:38:12,666
You'd have to go to the 
VLA in New Mexico to see that.

845
00:38:12,766 --> 00:38:15,633
This is a snapshot in time. 
This one's 10,000,000 years old.

846
00:38:15,733 --> 00:38:18,166
This one's 40,000,000 years old. 
Again, this is the simulation.

847
00:38:18,266 --> 00:38:21,300
So we're looking at it 
at a particular time.

848
00:38:21,400 --> 00:38:24,400
If everything were simple,

849
00:38:24,500 --> 00:38:26,500
as that basic 
model was assuming,

850
00:38:26,600 --> 00:38:29,533
this should all 
have the same color,

851
00:38:29,633 --> 00:38:32,933
should all have the same 
color frequency. It doesn't.

852
00:38:33,033 --> 00:38:34,833
Some of this is 
very high frequency.

853
00:38:34,933 --> 00:38:36,500
Some of this is 
very low frequency.

854
00:38:36,600 --> 00:38:38,200
That tells us that 
there's a lot going on.

855
00:38:38,300 --> 00:38:39,666
It's not that we 
didn't know this,

856
00:38:39,766 --> 00:38:41,566
but we're trying to 
better understand this.

857
00:38:41,666 --> 00:38:45,000
And over here is a measure 
of the shape of the spectrum.

858
00:38:45,100 --> 00:38:46,866
Again, the key thing 
is to look at the range

859
00:38:46,966 --> 00:38:48,700
of colors across this.

860
00:38:48,800 --> 00:38:50,666
These are just 
snapshots in time.

861
00:38:50,766 --> 00:38:52,466
I have a movie.

862
00:38:52,566 --> 00:38:54,233
This is kind of fun.

863
00:38:54,333 --> 00:38:56,000
It's a different color 
scale because we're still,

864
00:38:56,100 --> 00:38:57,766
this is still very much 
work under development,

865
00:38:57,866 --> 00:38:59,466
and Yi-Hao, the graduate 
student who's working

866
00:38:59,566 --> 00:39:01,833
on this changed the color scale. 
He likes this one better.

867
00:39:01,933 --> 00:39:04,400
I think it's kinda fun. 
We're watching time move here.

868
00:39:04,500 --> 00:39:07,366
This is the jet. 
This is inside a simulation.

869
00:39:07,466 --> 00:39:09,033
You're seeing the jet.

870
00:39:09,133 --> 00:39:11,633
The black hole is where that 
yellow stuff is spouting out.

871
00:39:11,733 --> 00:39:15,700
And again, the 
color coding here is

872
00:39:15,800 --> 00:39:18,566
that frequency where 
the spectrum turns over.

873
00:39:18,666 --> 00:39:21,066
The deep purple is 
below 100 megahertz,

874
00:39:21,166 --> 00:39:23,200
very low frequency, 
lower than we can see.

875
00:39:23,300 --> 00:39:25,633
And the blue is up 
at 10 gigahertz.

876
00:39:25,733 --> 00:39:27,766
I mean, the yellow's 
up at 10 gigahertz.

877
00:39:27,866 --> 00:39:31,233
So what you're seeing is an 
evolution of the spectrum

878
00:39:31,333 --> 00:39:33,333
of the radio source in time.

879
00:39:33,433 --> 00:39:35,600
Can't show it all at once, 
it'd just be too confusing.

880
00:39:35,700 --> 00:39:37,800
I mean, as it is, we're 
looking at a three-dimensional

881
00:39:37,900 --> 00:39:39,566
model here in 
two-dimensional space.

882
00:39:39,666 --> 00:39:43,500
The point is, you're watching 
it age before your very eyes.

883
00:39:43,600 --> 00:39:47,133
What the color coding here 
represents how it would look

884
00:39:47,233 --> 00:39:49,066
to us if we observed it 
in a radio telescope.

885
00:39:49,166 --> 00:39:51,633
So what we're trying 
to do is understand,

886
00:39:51,733 --> 00:39:53,666
better understand what 
the data we're getting out

887
00:39:53,766 --> 00:39:56,900
of this radio telescope 
in India actually mean.

888
00:39:58,533 --> 00:40:00,900
And it's going out to

889
00:40:01,000 --> 00:40:04,533
350,000,000 years, it goes 
out to 500,000,000 years.

890
00:40:04,633 --> 00:40:07,000
So this is a simulation 
over half a billion years

891
00:40:07,100 --> 00:40:08,800
of cosmic time.

892
00:40:09,933 --> 00:40:12,566
And we're trying to 
use this to inform,

893
00:40:12,666 --> 00:40:14,533
let's play it one 
more time real quick.

894
00:40:14,633 --> 00:40:17,066
There it is again. 
There's the jet.

895
00:40:17,166 --> 00:40:20,033
That's the galaxy, the active 
nucleus is very active.

896
00:40:20,133 --> 00:40:23,100
The black hole's running. 
We're at 3,000,000 years.

897
00:40:24,266 --> 00:40:26,800
It goes slowly at first 
and then shuts off.

898
00:40:26,900 --> 00:40:28,300
I think they shut 
off the black hole

899
00:40:28,400 --> 00:40:31,600
at about 10,000,000 years 
and then they speed up

900
00:40:31,700 --> 00:40:33,400
because we would 
be here all night

901
00:40:33,500 --> 00:40:36,266
if we watched it at this pace.

902
00:40:36,366 --> 00:40:37,766
It's 8,000,000 years.

903
00:40:37,866 --> 00:40:39,966
So you see that the 
yellow, there it goes,

904
00:40:40,066 --> 00:40:42,866
the black hole just shut off. 
The active nucleus shut off.

905
00:40:42,966 --> 00:40:44,733
Now it's passively evolving.

906
00:40:44,833 --> 00:40:49,033
So if we were to observe a real 
galaxy that was like this,

907
00:40:49,133 --> 00:40:52,900
this would be the relic, 
this would be the artifact.

908
00:40:53,000 --> 00:40:56,966
This would be what we dug up 
as the cosmic archeologists,

909
00:40:57,066 --> 00:40:58,400
that thing right there.

910
00:40:58,500 --> 00:41:00,100
A snapshot in time, 
that we, unfortunately,

911
00:41:00,200 --> 00:41:02,466
we can't see that in real life.

912
00:41:02,566 --> 00:41:04,500
It's only in the 
simulation that we're able

913
00:41:04,600 --> 00:41:06,133
to see that movie.

914
00:41:06,233 --> 00:41:09,800
But we're trying to use 
these simulations to inform

915
00:41:09,900 --> 00:41:12,900
what it is we are actually 
seeing in real life.

916
00:41:13,000 --> 00:41:15,766
So the trick is to 
take the observations

917
00:41:15,866 --> 00:41:17,933
that we're making with these 
radio telescopes and say,

918
00:41:18,033 --> 00:41:21,833
"All right, well, 
what is the best match?

919
00:41:21,933 --> 00:41:24,633
"What timing here 
does it best match

920
00:41:24,733 --> 00:41:26,500
"and how well can 
we determine that?"

921
00:41:26,600 --> 00:41:30,333
So that's where a lotta the 
work is going on right now.

922
00:41:35,266 --> 00:41:38,466
And this is what I was 
just talking about.

923
00:41:38,566 --> 00:41:40,500
What if we pretend the 
simulations are real?

924
00:41:40,600 --> 00:41:42,400
And what I mean by 
that is we can take--

925
00:41:42,500 --> 00:41:44,666
Those simulations have an 
enormous amount of information.

926
00:41:44,766 --> 00:41:46,866
You saw there's information 
about the shape of the spectrum,

927
00:41:46,966 --> 00:41:48,633
information about the 
slope of the spectrum,

928
00:41:48,733 --> 00:41:51,400
information about time, 
we have brightness of it.

929
00:41:51,500 --> 00:41:52,800
We have all these 
different qualities.

930
00:41:52,900 --> 00:41:55,066
We know what the 
pressure of the gas is.

931
00:41:55,166 --> 00:41:56,866
We know what the 
magnetic fields are,

932
00:41:56,966 --> 00:41:59,566
far more than we know in 
an actual, real observation.

933
00:41:59,666 --> 00:42:02,933
So to really try to make 
progress in understanding

934
00:42:03,033 --> 00:42:06,300
what it can tell us, we have 
to look at these simulations

935
00:42:06,400 --> 00:42:10,833
as though we were 
actually making a

936
00:42:10,933 --> 00:42:12,400
real observation.

937
00:42:12,500 --> 00:42:14,733
And that's what these 
are representing.

938
00:42:14,833 --> 00:42:17,000
So there are three 
simulations here.

939
00:42:17,100 --> 00:42:20,966
The 10,000,000 years, this one.

940
00:42:21,066 --> 00:42:23,200
50,000,000 years, these 
are snapshots in time

941
00:42:23,300 --> 00:42:24,933
of the simulation you saw.

942
00:42:25,033 --> 00:42:26,433
100,000,000 years.

943
00:42:26,533 --> 00:42:28,133
By the way, note the 
different size scale.

944
00:42:28,233 --> 00:42:29,766
It looks smaller,

945
00:42:29,866 --> 00:42:31,966
yet you saw it was 
getting bigger with time.

946
00:42:32,066 --> 00:42:33,933
That's just because it 
got too big to fit on here

947
00:42:34,033 --> 00:42:36,966
so I changed the size 
scale to fit it on there.

948
00:42:37,066 --> 00:42:38,766
So I'm just alerting 
people of that.

949
00:42:38,866 --> 00:42:41,466
Up here, this is an indication 
of that spectral shape,

950
00:42:41,566 --> 00:42:43,400
but let's go down here 
and look at the age.

951
00:42:43,500 --> 00:42:46,533
And it's a little difficult 
to see it scale on here

952
00:42:46,633 --> 00:42:49,133
with this large view.

953
00:42:49,233 --> 00:42:53,566
But this is, if we 
looked at a region

954
00:42:53,666 --> 00:42:57,466
of this radio source 
using the basic techniques

955
00:42:57,566 --> 00:42:59,200
I talked about when we 
first introduced them,

956
00:42:59,300 --> 00:43:02,166
when I introduced those 
simple radio spectra,

957
00:43:02,266 --> 00:43:04,200
this is how old it 
would tell us it is.

958
00:43:04,300 --> 00:43:09,000
So it would say that colors 
down here in this region

959
00:43:09,100 --> 00:43:11,000
are 8,000,000 years old.

960
00:43:11,100 --> 00:43:12,966
Colors out here are 
22,000,000 years.

961
00:43:13,066 --> 00:43:16,000
The actual simulation 
age, that's the nice 
thing about this.

962
00:43:16,100 --> 00:43:19,000
We know exactly how old 
this is because it's made up

963
00:43:19,100 --> 00:43:21,533
and we can test it, 
is 10,000,000 years.

964
00:43:21,633 --> 00:43:24,966
So it doesn't do 
too bad of a job,

965
00:43:25,066 --> 00:43:26,600
but here is one of the reasons

966
00:43:26,700 --> 00:43:28,700
why we are doing these 
simulations. Look at this.

967
00:43:28,800 --> 00:43:31,500
You saw this in the movie 
and some of the stills I did.

968
00:43:31,600 --> 00:43:33,000
This is a very different color.

969
00:43:33,100 --> 00:43:34,966
So 10,000,000 years 
is around here,

970
00:43:35,066 --> 00:43:36,633
so this should all 
be that blue color,

971
00:43:36,733 --> 00:43:38,033
but a lot of it is not.

972
00:43:38,133 --> 00:43:39,566
A lot of it looks much older.

973
00:43:39,666 --> 00:43:41,166
And we think we 
understand why that is.

974
00:43:41,266 --> 00:43:42,566
There are very good 
reasons for it.

975
00:43:42,666 --> 00:43:44,566
It's losing energy to 
blowing material around,

976
00:43:44,666 --> 00:43:46,200
a lot of other 
things are going on,

977
00:43:46,300 --> 00:43:47,900
but that's what we're 
trying to understand.

978
00:43:48,000 --> 00:43:51,433
And then out here, this should 
be 50,000,000 years old.

979
00:43:51,533 --> 00:43:55,266
That's way off the scale, so 
this time snapshot looks older.

980
00:43:56,733 --> 00:43:59,800
All of it looks older 
than it really is

981
00:43:59,900 --> 00:44:01,600
in the simulation.

982
00:44:01,700 --> 00:44:04,166
This one's not so bad.

983
00:44:04,266 --> 00:44:05,566
This should be 
100,000,000 years old.

984
00:44:05,666 --> 00:44:07,500
Most of it's that blue color.

985
00:44:07,600 --> 00:44:09,300
The point of this is 
that by doing this,

986
00:44:09,400 --> 00:44:14,033
we can better understand 
how good our deductions are

987
00:44:14,133 --> 00:44:16,733
about what we're learning, 
and ultimately be able

988
00:44:16,833 --> 00:44:18,600
to make corrections for that.

989
00:44:18,700 --> 00:44:21,000
So that's where we're 
going with this.

990
00:44:21,100 --> 00:44:24,066
All right. So where 
do we go from here?

991
00:44:24,166 --> 00:44:26,033
So we've made quite a 
bit of progress already.

992
00:44:26,133 --> 00:44:28,866
You can see the 
simulations are underway.

993
00:44:28,966 --> 00:44:31,233
Surveying of the 
radio is almost done.

994
00:44:31,333 --> 00:44:34,133
We're still working on doing 
the radio data reduction,

995
00:44:34,233 --> 00:44:36,733
whoops, back up.

996
00:44:36,833 --> 00:44:38,400
That's what this is over here.

997
00:44:38,500 --> 00:44:40,733
It's gonna be a little hard 
probably to see from the back,

998
00:44:40,833 --> 00:44:43,033
but these are two images 
of the same thing,

999
00:44:43,133 --> 00:44:45,166
just showing the progress 
we're slowly making.

1000
00:44:45,266 --> 00:44:47,166
This is a brand new telescope.

1001
00:44:47,266 --> 00:44:50,633
Nobody really knows exactly how 
to reduce the data from it yet.

1002
00:44:50,733 --> 00:44:53,433
Even the people who built 
it are still learning it, 
and so are we.

1003
00:44:53,533 --> 00:44:55,700
And there's a bit of 
an improvement, if you 
squint your eyes.

1004
00:44:55,800 --> 00:44:59,500
We measured it. There's 
some banding in the left 
panel here of this.

1005
00:44:59,600 --> 00:45:02,033
That is, there's some banding in 
here that's disappeared there.

1006
00:45:02,133 --> 00:45:05,633
So we're busy trying to 
figure that out, finish 
the observations,

1007
00:45:05,733 --> 00:45:07,600
and then later on go 
observe more of these.

1008
00:45:07,700 --> 00:45:10,166
After all this time, three 
observing runs a year

1009
00:45:10,266 --> 00:45:13,633
working on this, we've 
observed 40, which is a lot.

1010
00:45:13,733 --> 00:45:15,533
But there are a lot more to go.

1011
00:45:15,633 --> 00:45:17,833
And then I talked about 
these simulations.

1012
00:45:17,933 --> 00:45:19,566
I just showed you 
one simulation.

1013
00:45:19,666 --> 00:45:22,333
We learned a lot by doing that.

1014
00:45:22,433 --> 00:45:23,866
We're gonna do more.

1015
00:45:23,966 --> 00:45:25,433
For one thing, and 
it's gonna be done

1016
00:45:25,533 --> 00:45:27,000
on this thing called 
XSEDE, which is the

1017
00:45:27,100 --> 00:45:30,000
Extreme Science and Engineering 
Discovery Environment.

1018
00:45:30,100 --> 00:45:31,700
I'm glad they 
shortened it to XSEDE.

1019
00:45:31,800 --> 00:45:33,066
It's an NSF funded thing again.

1020
00:45:33,166 --> 00:45:35,833
Again, the NSF is 
supporting science of a lot

1021
00:45:35,933 --> 00:45:38,200
of different fields with 
this, and we've been awarded

1022
00:45:38,300 --> 00:45:41,166
3,000,000 core hours so far.

1023
00:45:41,266 --> 00:45:45,066
That sounds like a lot to me. 
I don't work in this normally.

1024
00:45:45,166 --> 00:45:46,300
Sebastian, he had to do this.

1025
00:45:46,400 --> 00:45:48,166
So that sounded 
impressive to me.

1026
00:45:48,266 --> 00:45:49,833
And it is.

1027
00:45:49,933 --> 00:45:53,766
It would take centuries 
on this laptop to do this.

1028
00:45:53,866 --> 00:45:56,666
And on this supercomputer, 
we're gonna run it in a month.

1029
00:45:56,766 --> 00:45:58,333
So 3,000,000 core 
hours for that.

1030
00:45:58,433 --> 00:46:02,000
And we're going to change the 
parameters of the material

1031
00:46:02,100 --> 00:46:04,700
into which these AGN jets go,

1032
00:46:04,800 --> 00:46:06,600
how they make those 
jets and lobes,

1033
00:46:06,700 --> 00:46:10,766
to better match the actual 
galaxies that we're observing.

1034
00:46:10,866 --> 00:46:13,400
We're gonna change 
the range of power

1035
00:46:13,500 --> 00:46:14,900
of the jet coming out of there.

1036
00:46:15,000 --> 00:46:16,433
Everything I showed you

1037
00:46:16,533 --> 00:46:18,700
was a great starting point, 
but it's one simulation.

1038
00:46:18,800 --> 00:46:22,033
So we're now gonna do a grid 
of nine in this next one

1039
00:46:22,133 --> 00:46:25,666
and better learn how 
these parameters affect

1040
00:46:25,766 --> 00:46:29,933
the results and what they 
mean for our interpretation

1041
00:46:30,033 --> 00:46:33,000
of how old our 
own real data are,

1042
00:46:33,100 --> 00:46:34,666
'cause that's what 
we're gonna do.

1043
00:46:34,766 --> 00:46:37,166
We're gonna try to measure 
how old these simulations are

1044
00:46:37,266 --> 00:46:40,000
when we know how old they are,

1045
00:46:40,100 --> 00:46:42,466
and then learn how we 
can better determine

1046
00:46:42,566 --> 00:46:46,733
the ages of our real AGN so 
we can connect those together.

1047
00:46:46,833 --> 00:46:48,666
And I haven't talked 
too much about the stars

1048
00:46:48,766 --> 00:46:50,433
since I first did the intro,

1049
00:46:50,533 --> 00:46:52,100
because we've been 
mostly focusing

1050
00:46:52,200 --> 00:46:55,400
on the active galactic nuclei 
and the radio observation.

1051
00:46:55,500 --> 00:46:57,333
But we have a lot of neat stuff

1052
00:46:57,433 --> 00:46:59,233
to look at those 
stellar populations,

1053
00:46:59,333 --> 00:47:02,966
to disentangle the 
different ages of the stars

1054
00:47:03,066 --> 00:47:04,733
and build up the history 
of star formation

1055
00:47:04,833 --> 00:47:07,300
across the entire galaxy.

1056
00:47:07,400 --> 00:47:11,900
And UW-Madison is 
a major partner in

1057
00:47:12,000 --> 00:47:13,833
something that's really cool.

1058
00:47:13,933 --> 00:47:18,233
The specific survey 
is called MaNGA,

1059
00:47:18,333 --> 00:47:21,300
stands for Mapping 
of Nearby Galaxies.

1060
00:47:21,400 --> 00:47:23,933
I bet they made the 
acronym up first

1061
00:47:24,033 --> 00:47:27,133
because the guy leading 
this at the time

1062
00:47:27,233 --> 00:47:29,000
was living and working in Japan.

1063
00:47:29,100 --> 00:47:32,066
So he thought, "Ah-ha,

1064
00:47:32,166 --> 00:47:34,100
"that's a good name for it."

1065
00:47:34,200 --> 00:47:37,400
It's part of something called 
the Sloan Digital Sky Survey.

1066
00:47:37,500 --> 00:47:39,700
If you haven't heard of 
that, keep an eye out for it.

1067
00:47:39,800 --> 00:47:42,966
It's been, I would say, one 
of the most important surveys

1068
00:47:43,066 --> 00:47:44,800
of the sky that 
humans have done.

1069
00:47:44,900 --> 00:47:47,066
It's been going on for 
close to 20 years now.

1070
00:47:47,166 --> 00:47:51,400
It's done with a rather 
modest-looking telescope.

1071
00:47:51,500 --> 00:47:54,000
That's it in the lower left. 
It's a weird thing.

1072
00:47:54,100 --> 00:47:56,300
I've never been out there, I've 
seen plenty of pictures of it,

1073
00:47:56,400 --> 00:47:58,000
but there's this 
enclosure around it.

1074
00:47:58,100 --> 00:48:03,200
It looks like it's a cannon 
with those pedals up there.

1075
00:48:03,300 --> 00:48:06,133
That's actually the 
opening of the light paths.

1076
00:48:06,233 --> 00:48:09,100
So the light goes in down 
that tube and all the 
detectors are down there.

1077
00:48:09,200 --> 00:48:11,266
It's not that big of a 
telescope by modern standards.

1078
00:48:11,366 --> 00:48:14,066
It's about 2 1/2 meters, 
but it is dedicated.

1079
00:48:14,166 --> 00:48:15,833
First it was dedicated 
to taking the images

1080
00:48:15,933 --> 00:48:17,633
of a major swath of the sky.

1081
00:48:17,733 --> 00:48:20,633
Those are all publicly 
available, anybody can 
go get that.

1082
00:48:20,733 --> 00:48:24,733
Since then, it's been dedicated 
to more specific activities,

1083
00:48:24,833 --> 00:48:26,966
a series of survey projects.

1084
00:48:27,066 --> 00:48:29,600
We're now in the fourth 
generation of this,

1085
00:48:29,700 --> 00:48:31,100
working on the fifth.

1086
00:48:31,200 --> 00:48:33,200
And UW's heavily involved 
in both of those.

1087
00:48:33,300 --> 00:48:36,933
The project scientist for 
all of this fourth generation

1088
00:48:37,033 --> 00:48:39,466
of Sloan is one of our faculty.

1089
00:48:39,566 --> 00:48:41,633
He's back right 
next door to Marsha,

1090
00:48:41,733 --> 00:48:44,100
who's the PI of our project, 
so he's in our building.

1091
00:48:44,200 --> 00:48:47,066
And we are also heavily 
involved in designing

1092
00:48:47,166 --> 00:48:49,400
one of the major projects for 
the next generation of this.

1093
00:48:49,500 --> 00:48:53,833
But on to this, 
this MaNGA survey

1094
00:48:53,933 --> 00:48:56,800
has been solving a problem 
that has bedeviled astronomers

1095
00:48:56,900 --> 00:48:58,566
who are doing things 
like I'm trying to do,

1096
00:48:58,666 --> 00:49:01,000
like our group is trying 
to do, for a long time,

1097
00:49:01,100 --> 00:49:04,633
in that a lot of what 
we observe in galaxies

1098
00:49:04,733 --> 00:49:09,233
with visible light is either 
from one part of the galaxy,

1099
00:49:09,333 --> 00:49:12,333
like the middle, 
or it's a swath,

1100
00:49:12,433 --> 00:49:14,666
a cut, 
through the galaxy,

1101
00:49:14,766 --> 00:49:17,633
because of the nature of the 
instruments that are used.

1102
00:49:17,733 --> 00:49:20,400
There are instruments 
that use optical fibers,

1103
00:49:20,500 --> 00:49:22,733
similar to what's in 
telecommunication.

1104
00:49:22,833 --> 00:49:24,866
Optical fibers are light pipes.

1105
00:49:24,966 --> 00:49:27,933
Hold up an optical fiber, 
whatever light comes in.

1106
00:49:28,033 --> 00:49:31,000
Goes down a pipe. You can 
bend them. Really cool.

1107
00:49:31,100 --> 00:49:32,666
Move the light, and 
it is a light pipe.

1108
00:49:32,766 --> 00:49:35,033
You can take the light 
from where it comes in

1109
00:49:35,133 --> 00:49:37,233
from the telescope, 
bend it around corners,

1110
00:49:37,333 --> 00:49:39,733
go down somewhere else, and 
run it into an instrument

1111
00:49:39,833 --> 00:49:41,900
like a spectrograph 
that makes the rainbow.

1112
00:49:43,233 --> 00:49:44,833
So what MaNGA's 
doing, and again,

1113
00:49:44,933 --> 00:49:46,633
this isn't the first time 
people have done this,

1114
00:49:46,733 --> 00:49:48,600
but this is done 
on a massive scale.

1115
00:49:48,700 --> 00:49:51,100
They're putting a whole bunch of 
these optical fibers together,

1116
00:49:51,200 --> 00:49:55,100
and the graphic on the right 
is meant to represent that.

1117
00:49:55,200 --> 00:49:58,866
You can see the hands in there 
are holding one of these things.

1118
00:49:58,966 --> 00:50:01,433
These are small, little devices.

1119
00:50:01,533 --> 00:50:04,466
That cylinder that 
that person is holding

1120
00:50:04,566 --> 00:50:07,166
contains dozens, it 
depends on which one,

1121
00:50:07,266 --> 00:50:11,700
we have different kinds of 
up to close to 130 fibers,

1122
00:50:11,800 --> 00:50:14,300
so dozens to over 
100 of these fibers.

1123
00:50:14,400 --> 00:50:17,100
If you look in the lower 
right corner there,

1124
00:50:17,200 --> 00:50:20,000
right here, this is a 
close-up of the top of that

1125
00:50:20,100 --> 00:50:21,333
with a little graphic done.

1126
00:50:21,433 --> 00:50:23,100
This is showing an 
overlay of a galaxy.

1127
00:50:23,200 --> 00:50:24,833
The idea is, here, 
you get the telescope,

1128
00:50:24,933 --> 00:50:26,466
make a picture of 
the galaxy here.

1129
00:50:26,566 --> 00:50:28,400
And every one of 
these little spots

1130
00:50:28,500 --> 00:50:30,266
is one of these optical fibers.

1131
00:50:30,366 --> 00:50:32,400
And it will take the light 
from each spot of the galaxy

1132
00:50:32,500 --> 00:50:35,366
and run it into the instrument, 
to the spectrograph,

1133
00:50:35,466 --> 00:50:36,933
and make a spectrum for us.

1134
00:50:37,033 --> 00:50:40,500
That allows us to look at 
these stellar populations

1135
00:50:40,600 --> 00:50:44,533
and other things about it 
across the entire galaxy,

1136
00:50:44,633 --> 00:50:46,266
not just at the center.

1137
00:50:46,366 --> 00:50:49,100
So this is a really 
important new development

1138
00:50:49,200 --> 00:50:50,833
and this is basically 
the second half

1139
00:50:50,933 --> 00:50:53,666
of the archeological dig, 
which we started on,

1140
00:50:53,766 --> 00:50:55,400
but haven't gotten very far yet

1141
00:50:55,500 --> 00:50:57,466
'cause we've been focusing on 
the simulations and the radio.

1142
00:50:57,566 --> 00:50:59,033
And this is just 
a quick example,

1143
00:50:59,133 --> 00:51:00,833
I'm gonna run through 
this very quickly,

1144
00:51:00,933 --> 00:51:02,333
of what this MaNGA can do.

1145
00:51:02,433 --> 00:51:03,933
This is putting 
everything together.

1146
00:51:04,033 --> 00:51:06,900
So here is, in the image 
down here in the lower left,

1147
00:51:07,000 --> 00:51:09,733
of a rather 
nondescript-looking galaxy.

1148
00:51:09,833 --> 00:51:12,066
This is from the original 
Sloan sky survey,

1149
00:51:12,166 --> 00:51:13,433
the one that took pictures.

1150
00:51:13,533 --> 00:51:16,066
This is a compendium 
of radio maps.

1151
00:51:16,166 --> 00:51:18,900
This is an overlay. 
There's the galaxy right there.

1152
00:51:19,000 --> 00:51:21,100
You can see it looks much 
more interesting in the radio.

1153
00:51:21,200 --> 00:51:23,100
These are those jets 
and plumes going out.

1154
00:51:23,200 --> 00:51:24,766
These are three 
different surveys

1155
00:51:24,866 --> 00:51:27,766
at two different frequencies, 
three different surveys.

1156
00:51:27,866 --> 00:51:29,833
This is not our data. 
These are existing ones,

1157
00:51:29,933 --> 00:51:31,800
but showing some of the 
complexity in there.

1158
00:51:31,900 --> 00:51:34,600
This is what we're trying 
to measure to determine 
the age of the AGN.

1159
00:51:34,700 --> 00:51:38,066
And this is a result of 
the MaNGA data product.

1160
00:51:38,166 --> 00:51:40,700
This is looking at 
actually ionized gas,

1161
00:51:40,800 --> 00:51:43,066
which is a little bit different 
from what I was telling you

1162
00:51:43,166 --> 00:51:46,100
about in figuring out 
the histories of stars,

1163
00:51:46,200 --> 00:51:48,733
but it's important for 
understanding what's 
going on right now.

1164
00:51:48,833 --> 00:51:50,533
So this will tell you about 
current star formation

1165
00:51:50,633 --> 00:51:52,633
and also what the active 
nucleus is doing as well

1166
00:51:52,733 --> 00:51:54,800
as looking at the radio.

1167
00:51:54,900 --> 00:51:57,933
And you can see here, I'm 
not gonna go into the details

1168
00:51:58,033 --> 00:51:59,966
of this, but you 
get in the past,

1169
00:52:00,066 --> 00:52:03,700
we might get something from 
just one part of the galaxy,

1170
00:52:03,800 --> 00:52:05,166
or a slit here.

1171
00:52:05,266 --> 00:52:08,000
Now we're able to see 
across the entire galaxy.

1172
00:52:08,100 --> 00:52:09,833
This is plotting 
where the ionized,

1173
00:52:09,933 --> 00:52:12,033
where we think is 
causing the ionized gas,

1174
00:52:12,133 --> 00:52:14,033
whether it's new star formation,

1175
00:52:14,133 --> 00:52:15,633
so it tells us about 
star formation,

1176
00:52:15,733 --> 00:52:17,033
or whether it's 
the active nucleus.

1177
00:52:17,133 --> 00:52:18,933
So that's just the 
tip of the iceberg

1178
00:52:19,033 --> 00:52:21,333
of what we're getting out 
of this MaNGA project.

1179
00:52:21,433 --> 00:52:23,333
All right.

1180
00:52:23,433 --> 00:52:26,433
To wrap up here, we've 
talked about a lot.

1181
00:52:26,533 --> 00:52:28,766
It's a complicated project.

1182
00:52:28,866 --> 00:52:31,300
It's a fun project, but there 
are a lotta pieces to it.

1183
00:52:31,400 --> 00:52:34,233
So let's just review it briefly.

1184
00:52:34,333 --> 00:52:37,266
And I'm going back to my little 
shtick from the beginning,

1185
00:52:37,366 --> 00:52:41,033
my silly little title for 
here, the time travel.

1186
00:52:41,966 --> 00:52:43,500
Again, that is--

1187
00:52:44,500 --> 00:52:46,200
It's not technically 
time travel,

1188
00:52:46,300 --> 00:52:48,333
what we're talking about, 
but it is an element of that.

1189
00:52:48,433 --> 00:52:49,833
That's what I said 
at the beginning.

1190
00:52:49,933 --> 00:52:52,066
This title has a 
grain of truth to it.

1191
00:52:52,166 --> 00:52:55,266
It's a time travel in 
the sense that by looking

1192
00:52:55,366 --> 00:52:58,133
at objects that are far away,

1193
00:52:58,233 --> 00:53:01,366
we are not seeing 
relics of them.

1194
00:53:01,466 --> 00:53:03,400
We are seeing them

1195
00:53:03,500 --> 00:53:06,700
as they were early in 
time, earlier in time.

1196
00:53:06,800 --> 00:53:08,433
That's the analogy with 
actually being able

1197
00:53:08,533 --> 00:53:12,133
to watch the residents of 
Pompeii on that fateful morning.

1198
00:53:13,166 --> 00:53:15,233
That's the time 
travel aspect of it.

1199
00:53:15,333 --> 00:53:17,500
We are also doing archeology.

1200
00:53:17,600 --> 00:53:20,333
That's looking into the 
relics of past events

1201
00:53:20,433 --> 00:53:23,500
in the histories of the 
galaxies, their stars,

1202
00:53:23,600 --> 00:53:25,233
their star formation history,

1203
00:53:25,333 --> 00:53:27,633
and what the supermassive 
black holes have been up to.

1204
00:53:27,733 --> 00:53:29,533
That's pretty tricky.

1205
00:53:29,633 --> 00:53:32,233
We can do it if the 
supermassive black holes

1206
00:53:32,333 --> 00:53:35,733
have been active and pumped 
out all of this hot gas,

1207
00:53:35,833 --> 00:53:38,933
this plasma, that is 
emitting radio light.

1208
00:53:39,033 --> 00:53:42,600
The spectrum, the 
rainbow of radio light,

1209
00:53:42,700 --> 00:53:45,833
encodes the history

1210
00:53:45,933 --> 00:53:48,700
of what that supermassive 
black hole's been doing.

1211
00:53:48,800 --> 00:53:51,966
It's up to us to figure 
out how to do it.

1212
00:53:52,066 --> 00:53:54,200
So the time traveling 
archeology aspect

1213
00:53:54,300 --> 00:53:57,833
is we're looking at 
galaxies as they were,

1214
00:53:57,933 --> 00:54:01,433
but also at artifacts back then

1215
00:54:01,533 --> 00:54:04,700
of even earlier epics 
to try to figure out,

1216
00:54:04,800 --> 00:54:07,433
the ultimate goal is to try 
to figure out this timing

1217
00:54:07,533 --> 00:54:10,700
between star formation 
and the activity

1218
00:54:10,800 --> 00:54:12,400
of the supermassive 
black hole to see

1219
00:54:12,500 --> 00:54:15,700
if we can really get 
some deep insight

1220
00:54:15,800 --> 00:54:17,566
into what people 
think is going on,

1221
00:54:17,666 --> 00:54:19,500
this deep connection 
of how the activity

1222
00:54:19,600 --> 00:54:21,800
of the supermassive 
black hole and the stars

1223
00:54:21,900 --> 00:54:24,000
in the galaxies are intimately 
connected to each other.

1224
00:54:24,100 --> 00:54:27,866
So it's part of that 
larger ongoing story.

1225
00:54:27,966 --> 00:54:31,766
And the final theme here, is 
lots of tools coming together.

1226
00:54:31,866 --> 00:54:34,600
That's what made this kind 
of a complex talk in a way,

1227
00:54:34,700 --> 00:54:37,033
but also a fun, fun project,

1228
00:54:37,133 --> 00:54:39,166
because we're using the 
state-of-the-art surveys.

1229
00:54:39,266 --> 00:54:40,733
I only briefly alluded 
to the radio ones,

1230
00:54:40,833 --> 00:54:42,833
but there's several of those, 
making good use of those.

1231
00:54:42,933 --> 00:54:45,500
I talked about the MaNGA survey.

1232
00:54:45,600 --> 00:54:47,566
We're using visible light.

1233
00:54:47,666 --> 00:54:49,266
That's how we're 
getting at the stars.

1234
00:54:49,366 --> 00:54:50,766
We're using radio light.

1235
00:54:50,866 --> 00:54:53,366
That's how we're getting 
primarily at the active nucleus.

1236
00:54:53,466 --> 00:54:55,800
And we're tying it all 
together with simulations

1237
00:54:55,900 --> 00:54:58,500
of the stars, and we talked 
a little bit about that.

1238
00:54:58,600 --> 00:55:00,600
But I alluded to it 
back in the beginning

1239
00:55:00,700 --> 00:55:03,333
when we're trying to 
disentangle what the spectrum,

1240
00:55:03,433 --> 00:55:05,066
what the rainbow of 
light of the galaxy was

1241
00:55:05,166 --> 00:55:07,900
in terms of how it was 
put together in the past.

1242
00:55:08,000 --> 00:55:09,633
When did the stars 
form to do that?

1243
00:55:09,733 --> 00:55:11,500
That's a modeling exercise.

1244
00:55:11,600 --> 00:55:14,100
And also, simulations of the 
jets and these big balloons,

1245
00:55:14,200 --> 00:55:16,133
these lobes, of the 
radio galaxies to try

1246
00:55:16,233 --> 00:55:18,500
to better understand 
what we're learning,

1247
00:55:18,600 --> 00:55:21,266
what we think we're learning, 
about the ages of them.

1248
00:55:22,566 --> 00:55:24,666
Thanks so much, appreciate it.

1249
00:55:24,766 --> 00:55:27,766
[applause]